dmaengine: move last completed cookie into generic dma_chan structure

Every DMA engine implementation declares a last completed dma cookie
in their private dma channel structures.  This is pointless, and
forces driver specific code.  Move this out into the common dma_chan
structure.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
[imx-sdma.c & mxs-dma.c]
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index 3296a73..d3ddcba 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -41,7 +41,6 @@
 	struct dma_chan			chan;
 	spinlock_t			lock;
 	struct dma_async_tx_descriptor	desc;
-	dma_cookie_t			last_completed;
 	enum dma_status			status;
 	int				dma_request;
 	struct scatterlist		*sg_list;
@@ -65,7 +64,7 @@
 {
 	if (imxdmac->desc.callback)
 		imxdmac->desc.callback(imxdmac->desc.callback_param);
-	imxdmac->last_completed = imxdmac->desc.cookie;
+	imxdmac->chan.completed_cookie = imxdmac->desc.cookie;
 }
 
 static void imxdma_irq_handler(int channel, void *data)
@@ -158,8 +157,8 @@
 
 	last_used = chan->cookie;
 
-	ret = dma_async_is_complete(cookie, imxdmac->last_completed, last_used);
-	dma_set_tx_state(txstate, imxdmac->last_completed, last_used, 0);
+	ret = dma_async_is_complete(cookie, chan->completed_cookie, last_used);
+	dma_set_tx_state(txstate, chan->completed_cookie, last_used, 0);
 
 	return ret;
 }